We propose to develop a novel volumetric specimen imager (VSI) device for significantly reducing breast lumpectomy's reoperation rate and improving outcomes. Among the annual performance of >200,000 lumpectomies in the US, up to 40%[1,2] of patients need a reoperation, when post-surgery pathology examination reveals positive margin, indicating incomplete tumor removal. Currently physicians rely on 2D specimen imaging for assessing margin status during surgery, which cannot adequately represent the 3D margin morphology[3]. We propose a next-generation VSI device that yields fully-3D images of the specimen with isotropic resolution, which can significantly improve margin assessment and provide precise guidance for immediate re-excision before closing wound. While conventional 3D imagers requires a long scan time (15- 30min.)[4] that disrupts surgical workflow, our VSI approach is enabled by a patented algorithm[6] that allows much faster imaging by substantially cutting down the amount of data to be collected[7], which offers high resolution 3D image within 2-3 minutes. In 4-5 years we plan to introduce VSI as the new standard of care for intra-operative lumpectomy margin assessment, which may reduce the re-excision rate to ~5% without unnecessary re-excision and mastectomy, thereby dramatically reducing healthcare costs and patient inconvenience while improving cosmetic outcomes. Our hypothesis for Phase I research is that the VSI can scan typical lumpectomy specimens within 3 minutes, yielding 3D images with over 90% margin-assessment sensitivity and specificity. The Specific Aims are: (1) to verify that image-quality requirements can be met by a calibrated VSI prototype, (2) to verify that scan-time requirements can be met by optimizing VSI parameters, and (3) To verify that VSI has higher sensitivity and specificity than SR for assessing lumpectomy margins. Reaching the above Aims will firmly establish the feasibility of VSI as a next-generation tool for 3D intra- operative margin assessment, and would reduce the technical risk of Phase II work, which include (1) fully optimization of VSI performance, (2) complete integration of the VSI to surgical workflow, and (3) larger-scale evaluation of VSI's clinical benefit with 200 lumpectomy specimens. In the US, about 6,000 surgical labs performing lumpectomy create an installed base estimated at $1B, among which large teaching programs and affiliated community hospitals are our lead customers, providing an early customer base of ~$7.5M.